Steam turbine clutch and method for disengagement of steam turbine from generator

ABSTRACT

A power generation system including: at least one elevated steam turbine receiving input steam at an elevated pressure and exhausting steam as low pressure steam; a low pressure steam turbine receiving low pressure steam exhausted from the elevated steam turbine, and a drive shaft for the low pressure steam turbine connected to a clutch which is reasonably coupled to a power generator, wherein the clutch has a first position in which power from the low pressure steam turbine is applied to the power generator and a second position in which power from the low pressure steam turbine is not applied to the generator.

BACKGROUND OF THE INVENTION

The present invention relates to power generation systems includingmultiple steam turbines and, particularly, to coupling steam turbines tosuch systems.

Large power generator systems often employ two or more steam turbines todrive generators to produce power. The steam turbines are conventionallycoupled together to drive power generators. For example, multiple steamturbines may be connected by a common shaft that drives a generator. Across compound turbine arrangement has two or more generators eachdriving one or more steam turbines. A power generation system havingcross-compound turbines typically has a generator for the high pressureand intermediate steam turbine, and a separate generator for the lowpressure steam turbines.

The power demand loads applied to power generator systems often varyduring the course of a day, weeks, and months. It is desirable for powergeneration systems to adapt to the variations in the power generationdemands. Specifically, there is a need for power generator systems toengage and disengage its steam turbines depending on the power demand.

BRIEF DESCRIPTION OF THE INVENTION

A system of valves and a clutch has been developed to disengage andengage one or more steam turbine sections from a power generationsystem. For example, the system may include a planetary clutch between alow pressure steam turbine and other steam turbines, and associatedvalves to open and turn off the steam flow to the low pressure steamturbine depending on whether the clutch engages or disengages the lowpressure steam turbine. The low pressure steam turbine may be disengagedwhile the demand for power from the generator is low and may be engagedwhen the demand for power is high.

A power generation system including: at least one elevated steam turbinereceiving input steam at an elevated pressure and exhausting steam aslow pressure steam; a low pressure steam turbine receiving low pressuresteam exhausted from the elevated steam turbine, and a drive shaft forthe low pressure steam turbine connected to a clutch which is reasonablycoupled to a power generator, wherein the clutch has a first position inwhich power from the low pressure steam turbine is applied to the powergenerator and a second position in which power from the low pressuresteam turbine is not applied to the generator.

The at least one elevated steam turbine may include a high pressuresteam turbine receiving high pressure steam and an intermediate steamturbine receiving steam exhausted from the high pressure steam turbine,wherein steam exhausted from the intermediate steam turbine is appliedas the low pressure steam for the low pressure steam turbine. The powergeneration system may further include a first low pressure steam valvein a conduit for low pressure steam flowing to the low pressure steamturbine and a second low pressure steam valve in a conduit for lowpressure steam flowing to a steam process extraction device, wherein thefirst low pressure steam valve is open while the second low pressuresteam valve is closed, and the first low pressure steam valve is closedwhile the second low pressure steam valve is open.

A power generation system has been developed comprising: a high pressuresteam turbine receiving high pressure steam and exhausting steam at anintermediate pressure; an intermediate steam turbine receiving steamexhausted from the high pressure steam turbine and exhausting lowpressure steam; a low pressure steam turbine receiving low pressuresteam exhausted from the intermediate steam turbine, and a drive shaftfor the low pressure steam turbine connected to a clutch and the clutchis releasably coupled to a power generator, wherein the clutch has afirst position in which power from the low pressure steam turbine isapplied to the power generator and a second position in which power fromthe low pressure steam turbine is not applied to the generator.

A method has been developed for power generation using a generator, anelevated pressure steam turbine, a low pressure steam turbine and aclutch coupled to a drive shaft of the low pressure steam turbine, themethod comprising: applying low pressure steam to the low pressure steamturbine; driving the generator by the low pressure steam turbine whilethe clutch is closed, and opening the clutch to disengage the lowpressure steam turbine from the generator.

The method may further comprise closing a first valve to terminate theapplication of low pressure steam to the low pressure steam turbine andopening a second valve to direct low pressure steam to a processextraction device, wherein the first valve is closed and the secondvalve is open while the clutch is open. In the method, the low pressuresteam turbine may be a first low pressure steam turbine and the methodfurther comprises: applying low pressure steam to the second lowpressure steam turbine during the application of low pressure steam tothe first low pressure steam turbine; driving the generator by thesecond low pressure steam turbine in addition to the driving of thegenerator by the first low pressure steam turbine, and continuing todrive the generator by the second low pressure steam turbine, while theclutch is open. Further, the opening of the clutch may disengage a driveshaft for the first low pressure steam turbine from a drive shaft forthe second low pressure steam turbine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a power generation system includingsteam turbines having a clutch coupling.

FIG. 2 is a schematic diagram of another power generation system similarto the power generation system shown in FIG. 1, except the other systemhas a single pair of low pressure steam turbines.

FIG. 3 is a schematic diagram of a cross-compound power generationsystem having a first drive shaft(s) with a high pressure steam turbineand an intermediate pressure steam turbine that collectively drive afirst generator, and a second drive shaft(s) with low pressure steamturbines that drive a second generator, wherein at least one of the lowpressure steam turbines is coupled by a clutch to the second driveshaft(s).

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic diagram of a power generation system 10 includingan electrical power generator 12 providing electricity to a load 13,such as an electrical power utility or grid. The generator isrotationally driven by a series of steam turbines including a highpressure steam turbine (HP) 14, an intermediate pressure steam turbine(IP) 16, a first pair of low pressure steam turbines (LPA) 18 and asecond pair of low pressure steam turbines (LPB) 20. The generator andsteam turbines are connected along a common drive shaft assembly 22,which may be two or more coaxial drive shafts coupled together.

High pressure steam, e.g., 2,500 pounds-per-square-inch (psi) at atemperature of 1,050 degrees Fahrenheit (566 degrees Celsius) from aboiler 13 is provided to the inlet of the high pressure steam turbine.The reaction blades (buckets) and steam passages in the high pressuresteam turbine tend to be small as compared to the reaction blades andsteam passages in the intermediate steam turbine. The reaction bladesand steam passages in the low pressure steam turbines tend to be largerthan those in the intermediate steam turbine. Steam exhausted from thehigh pressure turbine passes through a reheater 15, e.g., to be reheatedto 1,050 degrees Fahrenheit and flows to the intermediate pressure steamturbine. Low pressure steam, e.g., below 700 psi and preferably at orbelow 200 psi and 700 degrees Fahrenheit (370 degrees Celsius), isprovided from the intermediate pressure steam turbine 16 through a lowpressure steam conduit 30 to the low pressure steam turbines 18, 20.

A planetary clutch 24 couples the drive shafts of the pair of lowpressure turbines (LPA, LPB) 18, 20. The planetary clutch allows thesecond pair of low pressure turbines (LPB) to be disengaged from thefirst pair of low pressure turbines (LBA) 18 and the other steamturbines and generator 12 in the power generation system 10.

A first low pressure steam valve 32 and an isolation low pressure steamvalve 34 in the conduit 30 may be opened to allow steam to flow to thesecond pair of low pressure steam turbines 20 and closed to shut offsteam to the second pair of low pressure steam turbines. The isolationvalve 34 may have an open position and a closed, and no intermediatepositions. The first low pressure steam valve may have open and closedpositions, and intermediate positions to regulate the flow of lowpressure steam through the conduit 30 and to the low pressure steamturbine. These low pressure steam valves 32, 34 may be closed inconjunction with opening the clutch 24 to disengage the drive shaft ofthe second pair of low pressure steam turbines from the drive shafts ofthe other steam turbines. The second pair of low pressure steam turbines18 may be disengaged while the load 13 is relatively low and power fromthe second pair of steam turbines is not needed.

FIG. 2 shows a power generation system 40 similar to the powergeneration system 10, except with respect to the low pressure steamturbines 42. System 40 has a single pair of low pressure steam turbines42 having a drive shaft 44 coupled to a planetary clutch 46 that engagesthe drive shaft 22 of the intermediate pressure steam turbine 16. Afirst valve 48 governs the flow of steam to the pair of low pressuresteam turbines 42. A second valve 50 directs steam to an externalprocess 52, while the first valve is closed.

In operation, the first valve is open and the second valve is closedwhen the clutch is closed to couple the drive shaft 44 of the lowpressure steam turbines 42 to drive the generator 12 in cooperation withthe high pressure steam turbine 14 and the intermediate pressure steamturbine 16. When the load demand on the generator 12 is low, the lowpressure steam turbines 42 are disengaged by opening the clutch, closingthe first valve 48 to shut off the flow of low pressure steam to the lowpressure steam turbines and opening the second valve 50 to direct thelow pressure steam to a process extraction device 52, such as steamrecirculation conduits extending through a boiler providing steam forthe high pressure steam turbine or an other steam heated or drivendevice nearby the low pressure steam turbine.

FIG. 3 is a schematic diagram of a cross-compound power generationsystem 60 having a first drive shaft(s) 62 with a high pressure steamturbine 14 and an intermediate pressure steam turbine that collectivelydrive a first generator 64. The low pressure steam turbines include afirst pair of low pressure steam turbines 66 and a second pair of lowpressure steam turbines 68 are connected to a common drive shaft(s) 70that drive a second generator 72. A planetary clutch 74 allows the firstpair of low pressure steam turbines 66 to be disengaged from the secondpair of low pressure steam turbines and the generator. The first pair oflow pressure steam turbines may be disengaged when there is a low loaddemand on the second generator 72.

In conjunction with the operation of the clutch 74, valves are operatedto control the flow of low pressure steam from the intermediate pressuresteam turbine 16 to the low pressure steam turbines 66, 68 and to aprocess extraction device 52. First and second steam valves 76, 78 turnon and turn off low pressure steam to each, respectively, of the firstand second pairs of low pressure steam turbines. Both steam valves 76,78 are open to allow steam to flow to both pairs of low pressure steamturbines 66, 68, while the clutch is closed so that the common driveshaft(s) 70 are coupled together and both pairs of low pressure steamturbines 66, 68 drive the second generator 72. To disengage the firstpair of low pressure steam turbines, the clutch 74 is opened and thefirst steam valve 76 is closed to shut off low pressure steam to thefirst pair of low pressure steam turbines 66. When the first steam valve76 is closed, the second steam valve 78 remains open and the third steamvalve 80 is opened to direct low pressure steam to the processextraction device.

The clutch and low pressure steam valves disclosed herein may bearranged to disengage low pressure steam turbines during certainoperational conditions, such as when the load demand on the generator(s)is well below the capacity of the steam turbines that drive thegenerator(s). When the load is below capacity, the clutch and lowpressure steam valves may be operated to disengage at least one lowpressure steam turbine from the power generation system. The efficiencyof the system is increased by allowing the remaining low pressure steamturbine(s), if any, to operate at a higher power output and hence highercapacity than if all of the low pressure steam turbines were engaged andoperating at below capacity and hence lower efficiency. The disengagedsteam turbine can be idled so that it is ready to be reengaged to thepower system when needed, such as when the load demand increases.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. A power generation system comprising: at least one elevated steam turbine receiving input steam at an elevated pressure and exhausting steam as low pressure steam; a low pressure steam turbine receiving low pressure steam exhausted from the elevated steam turbine, and a drive shaft for the low pressure steam turbine connected to a clutch which is reasonably coupled to a power generator, wherein the clutch has a first position in which power from the low pressure steam turbine is applied to the power generator and a second position in which power from the low pressure steam turbine is not applied to the generator.
 2. The power generation system in claim 1 further comprising a first low pressure steam valve in a conduit for low pressure steam flowing to the low pressure steam turbine and a second low pressure steam valve in a conduit for low pressure steam flowing to a steam process extraction device, wherein the first low pressure steam valve is open while the second low pressure steam valve is closed, and the first low pressure steam valve is closed while the second low pressure steam valve is open.
 3. The power generation system in claim 1 wherein the low pressure steam turbine includes a first low pressure steam turbine, and a second low pressure steam turbine and the clutch engages and disengages the second low pressure steam turbine from the first low pressure steam turbine, and the first low pressure steam turbine is coupled to the generator.
 4. The power generation system in claim 3 further comprising a first low pressure steam valve in a conduit for the low pressure steam flowing to the second low pressure steam turbine, wherein the first low pressure steam valve is open while the clutch engages the second low pressure steam turbine to the first low pressure steam turbine, and the first low pressure steam valve is closed while the clutch disengages the second low pressure steam turbine from the first low pressure steam turbine.
 5. The power generation system as in claim 4 wherein the first valve is an isolation valve.
 6. The power generation system as in claim 1 wherein the at least one elevated steam turbine includes a high pressure steam turbine receiving high pressure steam and an intermediate steam turbine receiving steam exhausted from the high pressure steam turbine, wherein steam exhausted from the intermediate steam turbine is applied as the low pressure steam for the low pressure steam turbine.
 7. The power generation system as in claim 1 wherein the clutch is a planetary clutch.
 8. The power generation system as in claim 1 wherein the first position of the clutch is an open position and the second position of the clutch is a closed position.
 9. A power generation system comprising: a high pressure steam turbine receiving high pressure steam and exhausting steam at an intermediate pressure; an intermediate steam turbine receiving steam exhausted from the high pressure steam turbine and exhausting low pressure steam; a low pressure steam turbine receiving low pressure steam exhausted from the intermediate steam turbine, and a drive shaft for the low pressure steam turbine connected to a clutch and the clutch is releasably coupled to a power generator, wherein the clutch has a first position in which power from the low pressure steam turbine is applied to the power generator and a second position in which power from the low pressure steam turbine is not applied to the generator.
 10. The power generation system in claim 9 further comprising a first low pressure steam valve in a conduit for low pressure steam flowing to the low pressure steam turbine and a second low pressure steam valve in a conduit for low pressure steam flowing to a steam process extraction device, wherein the first low pressure steam valve is open while the second low pressure steam valve is closed, and the first low pressure steam valve is closed while the second low pressure steam valve is open.
 11. The power generation system in claim 10 wherein the low pressure steam turbine includes a first low pressure steam turbine and a second low pressure steam turbine, and the clutch engages and disengages the second low pressure steam turbine from the first low pressure steam turbine.
 12. The power generation system in claim 11 further comprising a first low pressure steam valve in a conduit for the low pressure steam flowing to the second low pressure steam turbine, wherein the first low pressure steam valve is open while the clutch engages the second low pressure steam turbine to the first low pressure steam turbine, and the first low pressure steam valve is closed while the clutch disengages the second low pressure steam turbine.
 13. The power generation system in claim 9 wherein the drive shaft is coupled to a drive shaft for the high pressure steam turbine and a drive shaft for the low pressure steam turbine.
 14. A method for power generation using a generator, an elevated pressure steam turbine, a low pressure steam turbine and a clutch coupled to a drive shaft of the low pressure steam turbine, the method comprising: applying low pressure steam to the low pressure steam turbine; driving the generator by the low pressure steam turbine while the clutch is closed, and opening the clutch to disengage the low pressure steam turbine from the generator.
 15. The method in claim 14 further comprising terminating the application of low pressure steam to the low pressure steam turbine while the clutch is open.
 16. The method in claim 14 further comprising closing a first valve to terminate the application of low pressure steam to the low pressure steam turbine and opening a second valve to direct low pressure steam to an external process, wherein the first valve is closed and the second valve is open while the clutch is open.
 17. The method as in claim 14 wherein the low pressure steam turbine is a first low pressure steam turbine and the method further comprises: applying low pressure steam to the second low pressure steam turbine during the application of low pressure steam to the first low pressure steam turbine; driving the generator by the second low pressure steam turbine in addition to the driving of the generator by the first low pressure steam turbine, and continuing to drive the generator by the second low pressure steam turbine, while the clutch is open.
 18. The method as in claim 17 wherein the opening of the clutch disengages a drive shaft for the first low pressure steam turbine from a drive shaft for the second low pressure steam turbine.
 19. The method as in claim 14 further comprising applying elevated pressure steam to an elevated pressure steam turbine and driving the generator with the elevated pressure steam turbine while the clutch is open.
 20. The method as in claim 14 further comprising, after the opening of the clutch, closing the clutch to engage the low pressure steam turbine to drive the generator. 